Security and safety are important and related factors that baffle the development and practicality of modern distributed system.However

most of researches on distributed system focus on security.Unfortunately

since software is being used largely in the complex distributed systems

the possibility of serious damage resulting from a software defect is considerable and growing

and then the complex distributed systems are plunging into safety crisis.In fact

distributed systems are in urgent need of new safety assurance technologies.After analyzing security and safety requirements of distributed system

we put forward new ideas for setting up the security and safety assurance structure of distributed system.We also analyze characteristics

designing aims for this structure.Since there are a lot of shortcomings in the current methods of realizing safety kernel (that is a new concept of safety assurance) in distributed system

we advance a program for RTOS to supply safety kernel mechanism.Based on all of these

we set up SADS (security and safety assurance structure of distributed system).At last

taking the control system in the traffic lights as example

prototype experiment of SADS has been done on the RT-Linux platform in the lab

and this experiment has proved the validity of SADS.